Incandescent lamp



May 49 1929., F R HOFFMAN 11,712,996

" INCANDESCENT LAMP Filed April 21, 1928 i Patent@ May 14, i929.

UN TE are.

FRED I. HOFFMAN, CHICAGG, ILLINOIS, ASSIGNOR T ROBERT A. /CJBIQTT, 0E

CHICAGO, ILLINOIS.

INCANDESCENT LAMP.

Application led April 21, 1928. Serial No. 2711,640.

The present invention has to do with im.- provements in incandescent lamps of the type making use of incandescent electric filaments. The features of the invention have reference to a construction and arrangement of incandescent lamps especially useful in connection wi-th miniature lamps such as are used for Christmas tree ornaments; but it will presently appear that the features of the invention 'are not limited in their usefulness to lamps of small size but may be also advantageously used in connection with larger units.

The features of the invention are also especially intended for use in connection with vacuum lamps in which the air is evacuated from the filament space so that the filament operates in a substantial vacuum. It will also appear however, that in this respect also the features of the invention are not limited but may be used to advantage in connection with lamps wherein the filament space is filled or occupied with some inert gas such as nitrogen or the like.

One object of the invention is to provide a lamp construction of great physical strength and which is capable of withstanding very severe use. In this connection it is an object to provide a lamp construction in which the glass bowl or globe may be made of great mechanical strength and ruggedness as distinguished from the very delicate and frail construction of these devices heretofore used.

In connection with the foregoing it is a further object of the invention to provide a construction which will establish within itself a very considerable degree of lens effect so as to greatly concentrate the strength of the light beam emitted. This feature is of especial value in connection with lamps intended for use in such devices as spot-lights and similar small portable outfits. lin connection with the foregoing it will be understood that these spot-lights and the like are generally so designed as to throw a relatively strong beam of light in a single direction and with a relatively small amount of diffusion.

A further feature of the invention relates to the provision of a construction in which a reflector is or may be directly incorporated with the lamp structure so as to constitute a permanent portion of the bulb. Such refiector when used is preferably incorporated directly into the lamp structure so as to constitute a permanent portion thereof.

Another object of the invention is to provide a lamp construction having a very rigid and rugged self-sup orting form of filament. Inthis connection Jdife filament is also so constructed that it lies substantially within a plane extending transversely of the lamp structure. This makes it possible to use a lamp structure in which the filament chamber is ver shallow and relatively broad. rIhe desira ility of this will become apparent from a further study and consideration. of the invention; and will also be evidentv when it is considered that the filament chamber lies almost entirely, if not wholly, within the physical confines of the metal shell.

Other objects and uses of the invention will appear from a detailed description of the same which consists in the features of construction and combinations of parts hereinafter described and claimed.

In the drawings:

Figure 1 shows a longitudinal section through one construction of lamp embodying the features of the present invention; the construction being one in which the filament space is evacuated through the glass stem, and in which the reflector is placed below or outside of the filament space;

Fig. 2 shows a view similar to that of Fig. l but illustrating a modified construction in which the reflector is placed within the vacuum space, and in which the vacuum space is evacuated from the floor of said space rather than through the stem;

Fig. 3 shows a view similar to that of Fig.

'2 with the exception that the vacuum space is evacuated from the side thereof instead of from the floor; y

Fig. 4 shows a longitudinal section through the glass bowl before being assembled;

Fig. 5 .shows a longitudinal section through the floor and stem element before being assembled; i

Fig. 6 shows a cross section through one of the reflectors; and

Fig. 7 shows a face view of the floor element looking in the general direct-ion of the arrows on the line 7 7 of Fig. 5.

Referring first to the construction shown in Fig. 1, the same includes the metal shell 10 which is spirally corrugated to provide the usual threads l1 for threading into the lamp socket. This shell is made of pressed sheet metal or in any other convenient manner.

|Ihe glass bulb 12 is of generally spherical form and the lower portion thereof is hollowed out as shown at 13 so as to establish a very shallowand more or less convex lament chamber 14.

The thickness of the glass layer 15 above this convex filament chamber is very great as ,compared to the usual bulb construction, and

in fact the amount of glass contained in this portion 15 is substantially equal to or greater than the hemisphere of glass of the bulb 12. This is evident when it is considered that the ,convex surface 13 of the filament chamber 14 v line 18; and above said line the bulb Surface 19 is cut back to some extent, a portion of the glass of the sphere; but, nevertheless, the body 15 of the glass is of very substantial thickness and strength.

The filament chamber 14 is very broad and shallow and substantially circular in form. The floor 20 thereof is formed by means of a glass plate or flange of slightly conical form. 'Ihe edge portion thereof is joined integrally with the reentrant flange portion 21 of the glass bulb member 12; and a collar 22 extends downwardly from the line of joinder between these parts and into the body of the metal shell 10.

Examination of Figs. 1, 2 and 3 in particular shows that the filament chamber 14 is of a generally frusto-conical' form, having a maximum diameter substantially at the line of joinder of 4the flange 21 with the thick body portion of the glass 12. It will also be noted that the flange portion 22 is of reduced diameter in the finally assembled article and is thus able to be set down easily into the shell 10. The upper edge of said shell therefore stands substantially at the point where the flange 21 joinsonto the thick glass portion 15 which is also the position of maximum diam-- eter of the filament chamber.

It is thus apparent that in the assembled lamp the only glass exposed above the Lipper end of the shell 10 is the very thick upper portion 15 which is therefore well able to withstand severe shocks and usage.

It is also noted that a considerable ortion of the body of the filament chamber itself is contained within the connes of the metal shell 10, and thatby lowering the floor 20 of the filament chamber a still larger portion of the filament chamber will be brought down into the body of the metal shield.

Another way of considering the matter is that a continuation or projection of the concave upper surface 13 of the filament chamber beyond its point of joinder with the flange 21 would carry it substantially to the upper edge of the metal shell 10 thus throwing into the body of the metal shell 10 substantially all of the filament chamber lying lower than the outer edge of the concave roof 13.

A relatively flattened filament 23, preferably of tungsten, is spread out in the filament. chamber so that it occupies a broad and shallow space. For this purpose said filament is preferably of a generally U-shaped form as shown in Fig. 7 with the parallel legs 24 and 25 lying relatively close together and extending a substantial distance across the width of the filament chamber and lying` within a plane therein.

The filament is sealed within a glass Stem 26 the upper end of which extends through and is sealed to the floor 2O of the filament chamber. The upper end 27 of this stem is sealed across, and the two ends of the filament wire or the lead in wires 28 and 29 are sealed through the upper end 27 as well shown in Fig. 5. It will be seen however, that the up. per portion of the tubular stem 26 reaches slightly up into the body of the filament chamber and above the floor 20 thereof.

In the construction of Fig. 1 the upper portionof the stem 26 is provided with an opening 3() which communicates with the filament chamber 14. In this case said lfilament chamber may be evacuated through the stem itself, after which the lower end 31 of said stem is Sealed to seal in the vacuum and also to seal in the Wires 28 and 29 as shown in Fig. 1.

In the construction of Fig. 2 thi` tubular stem 26 is sealed either at its upper or its lower end or both, and the filament space is evacuated through a special connection 32 which is afterwards sealed off leaving a small downwardly extending trat. In the construction of Fig. 3 the filament spara is evacuated through a side connection beyond the position of the collar 22, and is afterwards sealed off leaving a small teat 33. In this case also the tubular stem 26 is sealed either at its top or its bottom end or both so as {,)o avoid air leakage into the filament chamer. lT he relatively thick glass body 15 serves as a rather powerful lens to magnify tl e illuminating power of the filament and to more or less direct the illumination as a definite beam. In order to enhance the illumination and power of the lamp I prefer to place or form a reflector on or adjacent to the floor of the filament chamber. In some cases this may be done by coating either the inner or outer i surface of the flange 2O with a' reflecting material such as a mercury deposit. In other cases and preferably, a separate reflecting plate is set into place. This plate reflector when used is slightly coned to correspond with the form of the floor 20. Thusin Fig. 1 there is a reflecting plate 34 set up against the lower or `outside surface of the glass flange or floor 20, such plate therefore being outside of the vacuum space. In Figs. 2 and 3 on the other hand, the reflecting plate 35 is set into the lower portion of the vacuum space and against the top surface of the glass flange or floor 20 so that said reflecting .plate lies entirely within the vacuum space. In such case also such plate is preferably provided with an/upturned edge flange or lip 36 formed on the general slant or curve of the glass flaonge 21 ,and therefore serving to reinforce and protect such glass flange. In the construct-ion of 2 the reflecting plate is preferably provided with a small perforation immediat-ely above the position of the evacuating point 32 so as to allow the evacuation to proceed more readily and perfectly.

The downwardly depending collar 22 which is integral with the glass portions, sets down into the upper portion of the metal shell 10. Preferably its lower end 36a is beaded outwardly, leaving a relatively thin channel space between the flange 22 andthe inside of the metal shell 10. The entire glass unit, after being evacuated and sealed, is set down into the metal shell 10, the latter having been preferably filled .with plastic, cementitious material such as plaster of Paris, 37. This material will effectively seal the glass member into place, a portion of such material working its way up into the annular space between the flange 22 and the shell already referred to. Thus all portions of the glass member which lie within the confines of the metal shell will be effectively protected against damage, and the point of actual support will be carried up almost, or fully to the position of the thick glass portion 15.

Before the parts are sealed together by the material 37 a plate 38 is set down into the lower end of the metal shell 10 and against the inturned flange 39 thereof. This plate 38 carries a small central metal button 40 which is perforated to receive one of the terminal wires,.so that said terminal wire can be soldered to said button when the cementitious material has hardened. The other terminal wire is coldered to the outer` metal shell 10 in the usual manner.

Referring to Figs. 4, 5 and 6 I have therein illustrated a very convenient system of assemblage of the constituent glass parts. As

therein illustrated the glass member is first v. formed with a downwardly depending flangev 41 of the full diameter of the filament chamber 14, said flange 41 joining the body of the glass 15 substantially at the edge yof the concave surface 13. This flange 41 may also be initially beaded as shown at 42.

The floor-flange 20 is welded or sealed to.

the upper portion of the tubular stem 26, and the filament and leadin wires are sealed into the upper portion 27.

The unit shown in Fig. 5 may then be set up into position with respect to the unit of Fig. 4. If the reflector is to be placed inside of the filament chamber 14 it should be set against the top surface of the floor flange 2O before theparts are assembled. Otherwise said reflector` may be set up afterwards as in the case of the construction of the Fig. 1.

As the units of Figs. 4 and 5 have been brought together the flange 41 is drawn down to proper form and is sealed to the edge of the floor flange 20. Thereafter the filament space may be evacuated and the parts assembled into the metal shell.

The constructions shown in the present drawing are greatly enlarged as compared to the actual size of the lamps for use in Connection with spot lights, etc.; and it will be understood that the features of the invention may be used in connection with lamps either larger or smaller than illustrated in the present drawing.

While I have herein shown and described only certain embodiments ofthe features of my present invention still I do not intend to limit myself thereto except as I may do so in the claims.

I claim:

1. As a new article of manufacture an incandescent lamp comprising a base shell for engagement with a lamp socket, a glasslens element of generally spherical form and of greater diameter than the diameter of the shell seated in close proximity to the outer end of the shell and projecting beyond the same and with its center of sphere located beyond the plane of the end of the shell, said glass lens element being upwardly recessed to establish a filament chamber on the shell side of the glass lens element, the upper surface of said recess being concave downwardly and said surface lying entirely below the center of sphere of the glass lens element, conical floor establishing the lower portion of the filament chamber and having its edge portion sealed to the glass lens element on a circular line of joinder, a downwardly depending cylindrical flange sealed to said floor and to the glass lens element substantially at said line of joinder and reaching downwardly in the shell, a tubular stem reaching through the floor aforesaid into the filament chamber, terminal wires extending through said tubular stem and sealed thereinto and projecting into the filament chamber, a filament within the chamber connected to said terminal wires, and suitable cementing material filling the shell and engaging the flange aforesaid.

2. As a new'article of manufacture an incondescent lamp comprising a. base shell for engagement with a lamp socket, a glass lens element of generallyspherical form and of greater diameter than the diameter of the shell seated in close proximit to the outer end of the shell and projecting eyond the same and with its center of sphere located beyond theplane ofthe end of the shell, said glass lll() lens element being upwardly recessed to establish a filament chamber on the shell side of the glass lens element, the upper surface of said recess being concave downwardly and said surface lying entirely below the center of sphere of the glass lens element, a Yfloor establishing the lower portion of the filament chamber and having its edge portion sealed to the glass lens element, a tubular stem reaching through the Hoor aforesaid into the filament chamber, terminal Wires extending '.through said tubular stem and sealed therein- 'l to and projecting into the filament chamber,

a filament within the chamber connected to said terminal Wires, and sultable cementing cular form having its roof concave downwardly and having its lower portion reaching downwardly a substantial distance into the body of the shell, a lament located in said chamber, the roof of said chamber being very thick in proportion to the thickness of the filament chamber to thereby afford a maximum degree of mechanical strength.

FRED P. HOFFMAN. 

